Generally, a hydraulic excavator as a typical example of construction machines is constituted by an automotive lower traveling structure, an upper revolving structure which is swingably mounted on the lower traveling structure, and a working mechanism liftably mounted on the front side of the upper revolving structure. An engine for driving a hydraulic pump is mounted on a rear portion of a revolving frame of the upper revolving structure, and an exhaust gas purifying device for purifying exhaust gas by removing harmful substances in the exhaust gas is provided in an exhaust pipe of the engine.
Further, as an exhaust gas purifying device which is provided in a hydraulic excavator, a device is known which has a particulate matter removing filter (generally called a diesel particulate filter, abbreviated as DPF) for trapping and removing particulate matter (PM) in exhaust gas (Patent Literature 1: Japanese Patent Laid-Open No. 2003-120277 A).
The exhaust gas purifying device according to this Patent Literature 1, for example, is constituted by connecting in series an upstream cylinder connected to an exhaust pipe, a downstream cylinder which is disposed downstream of the upstream cylinder and from which exhaust gas is discharged, and a filter cylinder provided between the upstream cylinder and the downstream cylinder and incorporating a particulate matter removing filter therein. The exhaust gas purifying device has the filter cylinder fixed to the engine side, and the upstream cylinder and the downstream cylinder are detachably mounted on the filter cylinder. The particulate matter removing filter incorporated in the filter cylinder traps the particulate matter in the exhaust gas, and in the case where a predetermined amount of particulate matter has been trapped, the accumulated particulate matter is removed by burning it.
Accordingly, the exhaust gas purifying device is provided with pressure conduits which are respectively connected to the upstream side and the downstream side of the particulate matter removing filter in such a manner as to sandwich the particulate matter removing filter as well as a pressure sensor for detecting the upstream side pressure and the downstream side pressure supplied by the pressure conduits. In consequence, the exhaust gas purifying device detects the amount of particulate matter trapped (the clogged state) by the particulate matter removing filter from the pressure differential between the upstream side pressure and the downstream side pressure (Patent Literature 2: Japanese Patent Laid-Open No. 2005-120839 A).
Meanwhile, the particulate matter removing filter removes the particulate matter by burning it, but ash after burning gradually deposits. For this reason, with the pressure sensor of Patent Literature 1, the upstream cylinder and the downstream cylinder are detachably mounted on the filter cylinder incorporating the particulate matter removing filter so that the ash deposited in the particulate matter removing filter can be cleaned.
Nevertheless, according to the device according to Patent Literature 1, the filter cylinder incorporating the particulate matter removing filter is fixedly mounted to the engine. Accordingly, in the case where the ash deposited in the particulate matter removing filter is cleaned, the filter cylinder together with the upstream cylinder and the downstream cylinder must be dismounted from the engine, and the filter cylinder must be dismounted from the upstream cylinder and the downstream cylinder. For this reason, there is a problem in that much time and trouble are required in the cleaning operation of the particulate matter removing filter.
In addition, the exhaust gas purifying device is generally disposed in the vicinity of the engine in order that the exhaust gas can be treated in a high-temperature state. However, in the case of the hydraulic excavator, numerous equipments and parts, including a counterweight, a tank, a hydraulic pump, a hydraulic pipe, and a firewall partitioning the engine and the hydraulic pipe and the like, are disposed around the engine. Therefore, the counterweight, the tank, the engine, the firewall, and the like are disposed around and below the exhaust gas purifying device.
For this reason, the filter cylinder of the exhaust gas purifying device is dismounted by being moved upward and is remounted by being moved downward after the maintenance. In addition, the pressure sensor and the pressure conduits are generally mounted on the upper side of the exhaust gas purifying device in order that they are easily accessible in view of workability such as the connecting operation of the piping and the maintenance operation.
However, in the case where the pressure sensor and the pressure conduits are mounted on the upper side of the exhaust gas purifying device, the pressure sensor and the pressure conduits serve as obstacles when the exhaust gas purifying device is mounted or dismounted in the vertical direction. For this reason, it is necessary to dismount the pressure sensor, the pressure conduits, and the like in advance of the dismounting of the filter cylinder, and hence there is a problem in that the workability in the cleaning operation of the particulate matter removing filter deteriorates appreciably.